1. Field of the Invention
The present invention relates generally to diesel engines and more specifically to an improved swirl chamber arrangement for a swirl chamber type diesel engine.
2. Description of the Prior Art
FIG. 1 shows a prior art arrangement of the nature disclosed in JM-A-55-12054. As shown, this arrangement includes an essentially cylindrical or so called "disc" shaped swirl chamber 1 which is fluidly communicated with a main combustion chamber 2 via an angled transfer port 4. The swirl chamber 1 is further is formed with a nozzle throat 6 through which a fuel injector 8 injects fuel, and a bore 10 in which a glow plug 12 is disposed.
The transfer port 4 is arranged to introduce the compressed charge from the main combustion chamber 2 in the swirl chamber 1 in a manner that the incoming flow follows the path denoted by the bold arrow A. As shown in the drawing, due to the above mentioned flow of the air, the plume of fuel which is sprayed into the swirl chamber by the injector 8, is deflected (as indicated by arrow a) in a manner to flow through the swirl chamber in the direction denoted by the bold arrow B. Some of the fuel impinges on a wall portion of the nozzle throat and is deflected as indicated by arrow b.
However, this arrangement has suffered from the drawback that unacceptably large amounts of smoke tend to be formed during engine operation.
Experiments performed have established that the reason for the large amount of smoke formation is due to the fact that, during engine operation the spontaneous ignition of the fuel within the swirl chamber tends to occur at the point denoted by *.
Following the initial ignition, even though the swirl in the chamber is flowing in the opposite direction, the flame front travels rapidly back through the fuel spray in the direction denoted by the bold arrow C as well as propagating in the forward direction. This rearward propagation direction tends to cause the flame front to travel directy into the nozzle throat 6.
As the mixing effect of the air which is induced to swirl in the swirl chamber 1, is very low in the nozzle throat 6, localized combustion of a pocket of poorly carburetted excessively rich mixture occurs and leads to the formation of a large amount of smoke.